1. Field of the Invention
The present invention relates to a sheet feeding apparatus which can consistently separate and feed thin sheets in a facsimile, copying machine, or the like.
2. Related Background Art
In facsimile apparatus and the like, a plurality of sheets on the sheet supply plate are separated and fed one by one and the image drawn on the sheet is read by the reading section.
Namely, the frictional member comes into pressure contact with the conveying member which is rotating in the sheet conveying direction. The sheets are fed upstream to downstream the rotation of the conveying member. The sheets are separated one by one by the frictional force of the frictional member and sent to the reading section provided downstream.
In the apparatus having the construction as mentioned above, the relation of (.mu..sub.f &gt;.mu..sub.r &gt;.mu..sub.s) must be held to separate and feed the sheets, wherein .mu..sub.f denotes a coefficient of friction between the conveying belt and the sheet, .mu..sub.r is a coefficient of friction between the separating belt and the sheet, and .mu..sub.s is a coefficient of friction between the sheets. In general, a rubber material is used for the conveying belt and separating belt since it provides a high coefficient of friction. In the relation among the belts and the sheet, the values of those coefficients of frictions are determined using normal paper which will be most frequently used as a reference so as to satisfy the foregoing relation among the coefficients of the friction.
In the feeding apparatus having the construction as mentioned above, if the foregoing relation among the coefficients of frictions is not satisfied, the sheets will not be able to be consistently and separated or fed. However, the coefficients of friction largely vary due to the circumstances of the apparatus such as temperature, humidity, and the like in use. Therefore, there is the problem such that in spite of the face that the sheets could be separated and fed in a certain state, when the temperature and humidity change, the relationships among the coefficients of friction also varies, so that the sheets cannot be separated and fed.
On the other hand, in the case of the normal papers, even in the case where the relation of (.mu..sub.f &gt;.mu..sub.r) is held and the sheets can be consistently separated and fed, when the sheets having the smooth surfaces such as art papers, polyester films, or the like are used, there are the problems such that the sheets cannot be conveyed because the coefficient .mu..sub.r of friction between the separating belt and the sheet is larger than the coefficient .mu..sub.f of friction between the conveying belt and the sheet, and the like.